In the communications field, 60 GHz wireless communication pertains to millimeter wave communication. Generally, a millimeter wave refers to an electromagnetic wave whose wavelength is between 1 millimeter and 10 millimeters, corresponds to a frequency range from 30 GHz to 300 GHz, and is widely used in many fields, such as communication, radar, navigation, remote sensing, and astronomy.
Currently, license-exempt 60 GHz frequency bands allocated for China are only 5 GHz from 59 GHz to 64 GHz. According to the IEEE 802.11ad communications protocol, channel division is performed on a license-exempt frequency band. As shown in FIG. 1, there is only one type of channel bandwidth 2.16 GHz in channel division used in IEEE 802.11 ad, including channels numbered 1 to 4. The channels numbered 1 to 4 are referred to as large bandwidth channels; Chinese Working Group for Wireless Personal Area Network further divides the two physical channels numbered 2 and 3 into two 1.08 GHz channels 5 and 6 and two 1.08 GHz channels 7 and 8 respectively, and the channels numbered 5 to 8 are referred to as small bandwidth channels. In FIG. 1, channels 5 and 6 and channel 2, and channels 7 and 8 and channel 3 are different, but their frequencies overlap and these channels are co-channel interference channels with each other. For example, for channel 2, in addition to interference from its own large bandwidth (2.16 GHz) channel, there is also interference brought by the two small bandwidth (1.08 GHz) channels 5 and 6 that overlap channel 2.
Because a large number of co-channel interference problems exist in a densely-deployed network environment, a PCP/AP clustering mechanism is generally used to curb the co-channel interference problems. The PCP/AP clustering mechanism allows each cluster member PCP/AP to perform scheduling, so as to transmit a frame in a non-overlapping time period. There are two types of PCP/AP clustering mechanisms in IEEE 802.11 ad: a decentralized PCP/AP clustering mechanism and a centralized PCP/AP clustering mechanism.
A decentralized cluster enables nearby PCP/APs that run on a same channel to form a decentralized cluster. A PCP/AP in the cluster can receive a directional multi-gigabit beacon (DMG Beacon) frame and an announcement (Announce) frame that are transmitted by another PCP/AP and include scheduling information, so as to schedule communication in a non-overlapping time period and reduce interference between adjacent networks. The cluster includes a synchronization PCP/AP (S-PCP/S-AP) providing cluster synchronization information and control information. All members in the cluster use a DMG Beacon frame of the S-PCP/S-AP as a reference; the cluster members PCP/APs transmit a DMG Beacon frame within time of a group of Beacon SPs, so as to keep synchronized with the S-PCP/S-AP.
In the prior art, decentralized clustering includes two cases: becoming an S-PCP/S-AP and becoming a cluster member.
(1) A process of becoming an S-PCP/S-AP is specifically as follows: A PCP/AP transmits a DMG Beacon frame once at least every four BIs, where the DMG Beacon frame needs to include a Clustering Control (Clustering Control) field, setting of which meets a setting requirement of the S-PCP/S-AP.
(2) A process of joining a cluster with an identity of a cluster member is specifically as follows: After receiving a DMG Beacon frame transmitted by an S-PCP/S-AP, a PCP/AP listens on a channel; if finding that at least one Beacon SP is empty, randomly selects an empty Beacon SP to transmit the DMG Beacon and sets a BI, a length of a Beacon SP, a Cluster ID, and the like to same values as those of the S-PCP/S-AP, and in this case, the PCP/AP completes joining the decentralized cluster; if finding no empty Beacon SP, the PCP/AP cannot join the decentralized cluster.
However, the solution in the prior art also has the following disadvantage: The solution in the prior art provides only a co-channel decentralized PCP/AP clustering mechanism with equal bandwidth, and cannot resolve a problem concerning decentralized cluster establishment of a PCP/AP running on a 1.08 GHz small bandwidth channel and a PCP/AP running on a 2.16 GHz large bandwidth channel.